[SCSI] zfcp: Avoid referencing freed memory in req send

Avoid referencing a fsf request after sending it in fcp_fsf_req_send,
it might have already completed and deallocated.

Signed-off-by: Martin Petermann <martin@linux.vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>